JP2024048126A - Coil component, circuit board, electronic device, and method for manufacturing coil component - Google Patents

Abstract

[Problem] To provide a coil component, a circuit board, an electronic device, and a manufacturing method of a coil component that can eliminate stress distortion and reduce core loss. [Solution] The coil component includes a base, a coil conductor provided on the base, a first external electrode electrically connected to the coil conductor, a second external electrode electrically connected to the coil conductor, and a resin binder 36 that bonds the metal magnetic particles together. The base includes a first metal magnetic particle group and a second metal magnetic particle group. The first metal magnetic particle group is made of a plurality of first metal magnetic particles 31 each containing Fe and Si, and the second metal magnetic particle group is made of a plurality of second metal magnetic particles 41 each containing Fe and Si. The Si content of the first metal magnetic particles 31 is higher than the Si content of the second metal magnetic particles 41. The second average circularity of the second metal magnetic particle group is higher than the first average circularity of the first metal magnetic particle group. [Selected Figure] Figure 3

Description

The disclosure of this specification relates to coil components, circuit boards, electronic devices, and methods for manufacturing coil components.

Soft magnetic metal materials have been known as magnetic materials for coil components. Soft magnetic metal materials have a higher saturation magnetic flux density than ferrite materials, and are therefore particularly suitable as materials for the base of coil components through which large currents flow. The soft magnetic metal material is contained in the base in the form of metal magnetic particles. The metal magnetic particles are produced by granulating the soft magnetic metal material. The metal magnetic particles often have a particle size of several nm to several μm. An insulating film is provided on the surface of each metal magnetic particle contained in the base to prevent short circuits between adjacent metal magnetic particles.

The substrate containing the metal magnetic particles is produced through a compression molding process in which the mixed resin composition obtained by kneading the metal magnetic particles with a resin is poured into a molding die and pressure is applied to the mixed resin composition within the molding die.

The base of a coil component is required to have high magnetic permeability. As described in JP 2017-183655 (Patent Document 1), it is known that increasing the molding pressure in the compression molding process increases the filling rate of the metal magnetic particles contained in the base, thereby improving the magnetic permeability of the base. Patent Document 1 points out that low molding pressures result in low magnetic permeability of the base, and therefore a relatively high molding pressure of around 600 MPa is used in the compression molding process. The molding pressure can be changed depending on the required magnetic permeability, but traditionally it has been considered desirable to perform compression molding at a molding pressure of around 400 to 800 MPa.

JP 2017-183655 A

When a magnetic material containing metal magnetic particles is compression molded at a molding pressure of about 400 to 800 MPa, the metal magnetic particles contained in the magnetic material are deformed. For example, Figure 1 of Patent Document 1 shows a photograph of a cross section of a substrate containing deformed metal magnetic particles.

Low circularity metal magnetic particles deformed by compression molding or other processes experience large stress strain. In a base containing low circularity metal magnetic particles, there is a problem that the magnetic permeability decreases due to the stress strain occurring in the metal magnetic particles. When the magnetic material is compressed at a higher molding pressure, the stress strain occurring in the metal magnetic particles becomes larger, and the degree of decrease in the magnetic permeability of the base increases. Therefore, the improvement in magnetic permeability achieved by increasing the molding pressure is at least partially offset by the decrease in magnetic permeability due to the stress strain occurring in the metal magnetic particles. In addition, the deformation of the metal magnetic particles also causes the insulation between the metal magnetic particles to decrease. Therefore, when the molding pressure is increased to increase the magnetic permeability, there is a problem that the dielectric strength voltage of the magnetic base decreases. Furthermore, the greater the stress strain occurring in the metal magnetic particles, the greater the core loss.

To remove the stress strain generated in the metal magnetic particles, heat treatment at high temperatures (e.g., 600°C or higher) is required. However, a metal composite-type substrate in which the metal magnetic particles are bonded with a resin binder cannot be heated at a high enough temperature to remove the stress strain. For this reason, it is difficult to remove the stress strain of the metal magnetic particles contained in a metal composite-type substrate.

One of the objectives of the invention disclosed in this specification is to eliminate or alleviate at least one of the above problems. A more specific objective of the invention disclosed in this specification is to suppress the decrease in magnetic permeability and core loss caused by stress distortion occurring in metal magnetic particles.

Objects of the invention disclosed in this specification other than those mentioned above will become apparent by referring to the entire specification. The invention disclosed in this specification may solve problems that are understood from the description of this specification instead of or in addition to the above problems.

A coil component according to at least one embodiment of the present invention comprises a base, a coil conductor provided on the base, a first external electrode electrically connected to the coil conductor, and a second external electrode electrically connected to the coil conductor. In at least one embodiment of the present invention, the base includes a first metal magnetic particle group consisting of a plurality of first metal magnetic particles each containing Fe and Si and having a first average circularity, a second metal magnetic particle group consisting of a plurality of second metal magnetic particles each containing Fe and Si and having a second average circularity greater than the first average circularity, and a resin binder. In at least one embodiment of the present invention, the Si content in each of the plurality of first metal magnetic particles is higher than the Si content in each of the plurality of second metal magnetic particles.

According to at least one embodiment of the present invention, the decrease in magnetic permeability caused by stress distortion in metal magnetic particles is suppressed, thereby improving the magnetic permeability of the substrate and suppressing core loss.

FIG. 1 is a perspective view illustrating a coil component according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the coil component of FIG. 1 . FIG. 3 is an enlarged schematic view of a region A of the substrate shown in FIG. 2. FIG. 13 is a schematic diagram showing a cross section of a base body of a conventional coil component. FIG. 11 is a perspective view illustrating a coil component according to another embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating a coil component according to still another embodiment of the present invention. FIG. 11 is a front view illustrating a coil component according to still another embodiment of the present invention. FIG. 4 is a flow diagram showing a method for manufacturing a coil component according to an embodiment of the present invention. FIG. 4 is a flow diagram showing a method for manufacturing a base body of a coil component according to an embodiment of the present invention. 5A to 5C are schematic diagrams for explaining some steps of a manufacturing method for a coil component according to an embodiment of the present invention 5A to 5C are schematic diagrams for explaining some steps of a manufacturing method for a coil component according to an embodiment of the present invention. 5A to 5C are schematic diagrams for explaining some steps of a manufacturing method for a coil component according to an embodiment of the present invention. 5A to 5C are schematic diagrams for explaining some steps of a manufacturing method for a coil component according to an embodiment of the present invention.

Various embodiments of the present invention will be described below with reference to the drawings as appropriate. Note that components common to multiple drawings are given the same reference numerals throughout the multiple drawings. Please note that the drawings are not necessarily drawn to scale for ease of explanation. The embodiments of the present invention described below do not limit the invention according to the claims. The elements described in the following embodiments are not necessarily essential to the solution of the invention.

A coil component 1 according to one embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a perspective view showing the coil component 1, and Figure 2 is a schematic cross-sectional view of the coil component 1. As shown, the coil component 1 includes a base 10, a coil conductor 25 provided on the base 10, an external electrode 21 provided on the surface of the base 10, and an external electrode 22 provided on the surface of the base 10 at a position spaced apart from the external electrode 21. The base 10 includes a magnetic material.

In this specification, unless otherwise understood in the context, the "length" direction, "width" direction, and "thickness" direction of the coil component 1 are respectively the "L-axis" direction, the "W-axis" direction, and the "T-axis" direction in FIG. 1. The "thickness" direction is sometimes called the "height" direction. The L-axis, W-axis, and T-axis are perpendicular to each other.

The coil component 1 can be mounted on a mounting board 2a. The mounting board 2a is provided with land portions 3a and 3b. The coil component 1 is mounted on the mounting board 2a by joining the external electrode 21 to the land portion 3a and connecting the external electrode 22 to the land portion 3b. The circuit board 2 according to one embodiment of the present invention includes the coil component 1 and a mounting board 2a on which the coil component 1 is mounted. The circuit board 2 can be mounted on various electronic devices. Electronic devices on which the circuit board 2 can be mounted include smartphones, tablets, game consoles, automotive electrical equipment, servers, and various other electronic devices. For clarity of illustration, the mounting board 2a and the land portions 3a and 3b are omitted from illustrations other than FIG. 1.

The coil component 1 may be an inductor, a transformer, a filter, a reactor, or any other of various coil components. The coil component 1 may be a coupled inductor, a choke coil, or any other of various magnetically coupled coil components. The coil component 1 may be, for example, an inductor used in a DC/DC converter. The uses of the coil component 1 are not limited to those explicitly stated in this specification.

The base 10 is made of a magnetic material and has a generally rectangular parallelepiped shape. In one embodiment of the present invention, the base 10 is configured so that the dimension in the L-axis direction (length dimension) is greater than the dimension in the W-axis direction (width dimension) and the dimension in the T-axis direction (height dimension). For example, the length dimension is in the range of 1.0 mm to 6.0 mm, the width dimension is in the range of 0.5 mm to 4.5 mm, and the height dimension is in the range of 0.5 mm to 4.5 mm. The dimensions of the base 10 are not limited to the dimensions specifically described in this specification. In this specification, the term "rectangular parallelepiped" or "rectangular parallelepiped shape" does not mean only "rectangular parallelepiped" in the mathematically strict sense. The dimensions and shape of the base 10 are not limited to those explicitly described in this specification.

The base 10 has a first main surface 10a, a second main surface 10b, a first end surface 10c, a second end surface 10d, a first side surface 10e, and a second side surface 10f. The outer surface of the base 10 is defined by these six surfaces. The first main surface 10a and the second main surface 10b form the surfaces at both ends of the height direction of the base 10, the first end surface 10c and the second end surface 10d form the surfaces at both ends of the width direction of the base 10, and the first side surface 10e and the second side surface 10f form the surfaces at both ends of the length direction of the base 10. The upper surface 10a and the lower surface 10b are spaced apart by the height dimension of the base 10, the first end surface 10c and the second end surface 10d are spaced apart by the width dimension of the base 10, and the first side surface 10e and the second side surface 10f are spaced apart by the length dimension of the base 10. As shown in FIG. 1, the first main surface 10a is located on the upper side of the base body 10, and therefore the first main surface 10a is sometimes referred to as the "upper surface." Similarly, the second main surface 10b is sometimes referred to as the "lower surface." The coil component 1 is disposed so that the second main surface 10b faces the substrate 2, and therefore the second main surface 10b is sometimes referred to as the "mounting surface."

In one embodiment of the present invention, the external electrode 21 is provided on the mounting surface 10b and the end surface 10c of the base 10. The external electrode 22 is provided on the mounting surface 10b and the end surface 10d of the base 10. The external electrodes 21 and 22 are arranged spaced apart from each other in the length direction. The shape and arrangement of each of the external electrodes 21 and 22 are not limited to the example shown in the figure. The external electrodes 21 and 22 may be formed by applying a conductive paste to the surface of the base 10. This conductive paste contains metal particles with excellent conductivity, such as Ag and Cu. The external electrodes 21 and 22 may include a plating layer. This plating layer may be two or more layers. The two plating layers may include a Ni plating layer and a Sn plating layer provided on the outside of the Ni plating layer.

The coil conductor 25 has a winding portion 25A wound around a coil axis Ax extending along the thickness direction (T-axis direction), a lead-out portion 25B connecting one end of the winding portion 25A to the external electrode 21, and a lead-out portion 25C connecting the other end of the winding portion 25A to the external electrode 22. In the illustrated embodiment, only both ends of the coil conductor 25 are exposed from the base 10, and the other portions are provided within the base 10. In the illustrated embodiment, the coil axis Ax intersects with the first main surface 10a and the second main surface 10b, but does not intersect with the first end surface 10c, the second end surface 10d, the first side surface 10e, and the second side surface 10f. In other words, the first end surface 10c, the second end surface 10d, the first side surface 10e, and the second side surface 10f extend along the coil axis Ax. In one embodiment, the coil axis Ax passes through the intersection of two diagonals of the base 10 when the base 10 is viewed in a plan view. The shape of the coil conductor 25 is not limited to that shown in the figure. For example, the coil conductor 25 may be wound around the coil axis Ax for fewer than one turn when viewed in a plan view (when viewed from the T-axis direction). The shape of the coil conductor 25 when viewed in a plan view may be an ellipse, a meandering shape, a straight line, or a combination of these.

In this specification, the region of the base 10 inside the winding portion 25A when viewed from the direction of the coil axis Ax is referred to as the core region 10X, and the region outside the winding portion 25A is referred to as the margin region 10Y. Even if the coil conductor 25 is wound around the coil axis Ax less than one turn in a plan view, if there is a portion that winds around the coil axis Ax by more than 2/3 (more than 240° in a plan view), the portion that winds around by more than 2/3 can be regarded as the winding portion 25A, and the region of the base 10 inside the winding portion of the coil conductor 25 with less than one turn can be regarded as the core region 10X, and the outer portion can be regarded as the margin region 10Y.

When the coil conductor 25 does not have a portion that wraps around the coil axis Ax by more than 2/3 of a turn (more than 240° in plan view), but has a portion that extends circumferentially by more than 2/3 of a turn around an axis that extends parallel to the T axis (for example, when the shape of the coil conductor 25 in plan view is a meandering shape), the region of the base 10 that is inside the portion that extends around the axis by more than 2/3 of a turn in the radial direction (the radial direction perpendicular to the axis and centered on the axis) can be regarded as the core region 10X, and the region outside of that can be regarded as the margin region 10Y. If the coil conductor 25 does not have a portion that wraps around the coil axis Ax for more than 2/3 of a turn, and if the coil conductor 25 does not have a portion that extends circumferentially for more than 2/3 of a turn around any axis that extends parallel to the T-axis (for example, if the shape of the coil conductor 25 in a plan view is linear), there is no area in the base 10 that can be considered to be the core region 10X or the margin region 10Y.

The surface of the coil conductor 25 may be covered with an insulating coating made of an insulating material with excellent insulating properties. This insulating coating may be made of a resin with excellent insulating properties, such as polyurethane, polyamide-imide, polyimide, polyester, or polyester-imide. The base 10 may have a substrate made of an insulating material with excellent insulating properties, and the coil conductor 25 may be formed on this substrate.

In one embodiment of the present invention, the base 10 is composed of a magnetic material containing a plurality of metal magnetic particles. The microstructure of the base 10 will be described with reference to FIG. 3. FIG. 3 is an enlarged cross-sectional view that shows a schematic enlargement of the cross section of the base 10. Specifically, FIG. 3 shows an enlargement of region A shown in FIG. 2. FIG. 2 shows a cross section of the coil component 1 cut along a plane passing through the coil axis Ax, and region A shows a portion of the cross section of the base 10 shown in FIG. 2.

3, the substrate 10 in one embodiment includes a plurality of first metal magnetic particles 31 and a plurality of second metal magnetic particles 41. In this specification, the plurality of first metal magnetic particles 31 contained in the substrate 10 may be collectively referred to as a first metal magnetic particle group, and the plurality of second metal magnetic particles 41 contained in the substrate 10 may be collectively referred to as a second metal magnetic particle group. In other words, the first metal magnetic particle group is composed of a plurality of first metal magnetic particles 31, and the second metal magnetic particle group is composed of a plurality of second metal magnetic particles 41. In this specification, when it is not necessary to distinguish between the first metal magnetic particles 31 and the second metal magnetic particles 41 in the context, for the sake of simplicity, both may be collectively referred to as "metal magnetic particles".

The first metal magnetic particle 31 and the second metal magnetic particle 41 are each composed of a soft magnetic metal material. The first metal magnetic particle 31 and the second metal magnetic particle 41 each contain Fe and Si. In some embodiments, the content of Si in the second metal magnetic particle 41 is smaller than the content of Si in the first metal magnetic particle 31. As the soft magnetic metal material for the first metal magnetic particle 31 and the second metal magnetic particle 41, for example, (1) alloy-based Fe-Si-Cr, Fe-Si-Al, Fe-Si-B-P-Cu, (2) amorphous Fe-Si-Cr-B-C or Fe-Si-B-Cr, or (3) a mixed material thereof can be used. The soft magnetic metal material for the first metal magnetic particle 31 and the second metal magnetic particle 41 is not limited to the above. For example, the soft magnetic metal material for the first metal magnetic particle 31 and the second metal magnetic particle 41 can contain at least one element of Zr, Nb, Cu, and P in addition to the above elements. In at least one embodiment of the present invention, the sum of the Fe content in the first metal magnetic particles 31 and the Fe content in the second metal magnetic particles 41 is 80 wt % or more.

In at least one embodiment of the present invention, the composition of the first metal magnetic particle 31 may be different from the composition of the second metal magnetic particle 41. For example, the first metal magnetic particle 31 may contain an element that is not contained in the second metal magnetic particle 41. For example, both the first metal magnetic particle 31 and the second metal magnetic particle 41 contain Fe and Si, but only one of them may contain any one of Nb, Cu, and Cr. For example, each of the first metal magnetic particles 31 constituting the first metal magnetic particle group may contain Fe, Si, Nb, Cu, B, and C, and each of the second metal magnetic particles 41 constituting the second metal magnetic particle group may contain Fe, Si, Cr, B, and C. In this case, the Nb and Cu contained in the first metal magnetic particle 31 are not contained in the second metal magnetic particle 41, and the Cr contained in the second metal magnetic particle 41 is not contained in the first metal magnetic particle 31. Thus, in at least one embodiment, the first metal magnetic particles 31 can be distinguished from the second metal magnetic particles 41 based on the difference in the elements they contain.

In at least one embodiment of the present invention, the first metal magnetic particle 31 may be distinguishable from the second metal magnetic particle 41 based on the difference in the composition ratio of elements contained in both the first metal magnetic particle 31 and the second metal magnetic particle 41. For example, in at least one embodiment of the present invention, when both the first metal magnetic particle 31 and the second metal magnetic particle 41 contain Si, the content ratio of Si in the first metal magnetic particle 31 may be higher than the content ratio of Si in the second metal magnetic particle 41. In at least one embodiment of the present invention, the content ratio of Si in the first metal magnetic particle 31 is 2 wt% or more. The content ratio of Si in the second metal magnetic particle 41 is smaller than the content ratio of Si in the first metal magnetic particle 31, for example, 0.5 wt% to 2.0 wt%.

In at least one embodiment of the present invention, the strength of each of the first metal magnetic particles 31 is higher than the strength of each of the second metal magnetic particles 41. For example, by making the Si content ratio in the first metal magnetic particles 31 higher than the Si content ratio in the second metal magnetic particles 41, the strength of each of the first metal magnetic particles 31 can be made higher than the strength of each of the second metal magnetic particles 41. This makes it possible to suppress deformation of the first metal magnetic particles 31, which are susceptible to the action of molding pressure, when the base 10 is produced by a compression molding process.

In this specification, the "strength" of a metal magnetic particle may mean the deformation strength when plastic deformation occurs in the metal magnetic particle, or the deformation strength when elastic deformation occurs in the metal magnetic particle. The deformation strength of a metal magnetic particle represents the strength required for deformation when the metal magnetic particle is compressed. The strength of a metal magnetic particle is an index that represents the resistance of the metal magnetic particle to deformation, and means, for example, the deformation strength measured according to JIS Z 8844:2019. The strength of the first metal magnetic particle 31 and the second metal magnetic particle 41 can be measured by a commercially available compression tester (for example, MCT510 provided by Shimadzu Corporation). For example, the deformation strength for a compression displacement of 10% of the particle diameter is obtained for each of the multiple first metal magnetic particles 31, and the average value of the deformation strength for each particle can be used as the strength of the first metal magnetic particle 31. Similarly, the deformation strength for a compressive displacement of 10% of the particle diameter is obtained for each of the plurality of second metal magnetic particles 41, and the average value of the deformation strength for each particle can be taken as the strength of the second metal magnetic particles 41. The strength of the first metal magnetic particles 31 and the second metal magnetic particles 41 can also be determined by measuring the Vickers hardness on a cross section exposed by cutting the base 10 along the T-axis direction, and the measured Vickers hardness can be taken as the strength. In this case, the Vickers hardness is measured by selecting metal magnetic particles contained in the base 10 that are 5 μm or more in size, and the selected particles. The Vickers hardness can be measured by a commercially available micro Vickers hardness tester (for example, MMT-X7 provided by Matsuzawa Co., Ltd.). In at least one embodiment of the present invention, the strength of each of the first metal magnetic particles 31 is higher than the strength of each of the second metal magnetic particles 41, so that the first metal magnetic particles 31 are less likely to deform than the second metal magnetic particles 41. Therefore, when the base 10 is produced by, for example, a compression molding method, the deformation of the first metal magnetic particles 31 is suppressed. By increasing the content ratio of Si in the metal magnetic particles, the strength of the metal magnetic particles can be increased. In addition, by using an amorphous material as the magnetic material of the metal magnetic particles, the strength of the metal magnetic particles can be increased. By heating the amorphous metal magnetic particles, metal magnetic particles that are partially crystalline and the remaining portion amorphous can be formed. Such partially crystalline metal magnetic particles also have high strength. In at least one embodiment of the present invention, the strength of each of the first metal magnetic particles 31 and the strength of each of the second metal magnetic particles 41 are each set to 500 MPa or more. In at least one embodiment of the present invention, the strength of each of the first metal magnetic particles 31 and the Vickers hardness of each of the second metal magnetic particles 41 are each set to 1000 Hv or more.

In at least one embodiment of the present invention, the average particle size of the first metal magnetic particles 31 contained in the base 10 (i.e., the average particle size of the first metal magnetic particle group) is larger than the average particle size of the second metal magnetic particles 41 contained in the base 10 (i.e., the average particle size of the second metal magnetic particle group). In at least one embodiment of the present invention, the average particle size of the first metal magnetic particles 31 is more than twice as large as the average particle size of the second metal magnetic particles 41. The average particle size of the first metal magnetic particles 31 is, for example, 4 μm to 30 μm. The average particle size of the second metal magnetic particles 41 is, for example, 0.2 μm to 6 μm. In this specification, the average particle size of the first metal magnetic particle group may be referred to as the first average particle size, and the average particle size of the second metal magnetic particle group may be referred to as the second average particle size. The first average particle size and the second average particle size may be obtained, for example, as follows. First, the base 10 is cut along the T-axis direction to expose the cross section, and the cross section is photographed at a magnification of 2000 times to 5000 times with a scanning electron microscope (SEM) to obtain an SEM image. Also, SEM-EDS mapping is performed within the field of view of this SEM image to identify the first metal magnetic particles 31 and the second metal magnetic particles 41. For example, since the first metal magnetic particles 31 have a higher Si content than the second metal magnetic particles 41, the metal magnetic particles contained in the base 10 can be divided into the first metal magnetic particles 31 and the second metal magnetic particles 41 based on whether the Si content is greater than a predetermined value. Then, in the SEM image, the particle size distribution of the first metal magnetic particles 31 (for example, a volume-based particle size distribution) is obtained, and the 50% value (D50) of this particle size distribution can be taken as the average particle size (first average particle size) of the first metal magnetic particle group. Similarly, in the SEM image, the particle size distribution of the second metal magnetic particles 41 is obtained, and the 50% value of this particle size distribution can be taken as the average particle size (second average particle size) of the second metal magnetic particle group. In at least one embodiment of the present invention, the first average particle size is five times or more larger than the second average particle size. According to at least one embodiment of the present invention, the base 10 includes a plurality of first metal magnetic particles 31 having a first average particle size and a plurality of second metal magnetic particles having a second average particle size smaller than the first average particle size, so that the second metal magnetic particles 41 penetrate between the first metal magnetic particles 31, thereby increasing the filling rate of the metal magnetic particles in the base 10.

In some embodiments, the base 10 contains more first metal magnetic particles 31 than second metal magnetic particles 41 in terms of mass ratio. In at least one embodiment of the present invention, the base 10 contains the first metal magnetic particle group and the second metal magnetic particle group in a weight ratio range of 60:40 to 80:20. That is, when the total mass of the first metal magnetic particle group and the second metal magnetic particle group in the base 10 is 100 wt%, the base 10 contains the first metal magnetic particle group in a range of 60 to 80 wt% and the second metal magnetic particle group in a range of 20 to 40 wt%. Thus, in the base 10, the weight ratio of the first metal magnetic particle group is greater than the weight ratio of the second metal magnetic particle group. By containing a large number of large-diameter first metal magnetic particles 31 in terms of mass ratio, the magnetic permeability of the base 10 can be increased.

In at least one embodiment of the present invention, the base 10 may include a plurality of third metal magnetic particles (not shown) in addition to the plurality of first metal magnetic particles 31 and the plurality of second metal magnetic particles 41. The plurality of third metal magnetic particles contained in the base 10 may be collectively referred to as a third metal magnetic particle group. The average particle size of the plurality of third metal magnetic particles may be smaller than the average particle size (second average particle size) of the plurality of second metal magnetic particles 41. For example, the particle size of the plurality of third metal magnetic particles is 0.75 times or less of the second average particle size. The average particle size of the plurality of third metal magnetic particles (i.e., the average particle size of the third metal magnetic particle group) is, for example, 0.1 μm to 3 μm. In at least one embodiment of the present invention, the base 10 may contain the third metal magnetic particle group in a range of 0 to 5 wt % when the total mass of the first metal magnetic particle group, the second metal magnetic particle group, and the third metal magnetic particle group is 100 wt %. The composition of the third metal magnetic particles may be different from both the composition of the first metal magnetic particles 31 and the composition of the second metal magnetic particles 41. In this case, the third metal magnetic particles can be distinguished from the first metal magnetic particles 31 and the second metal magnetic particles 41 based on the difference in the elements contained therein. The third metal magnetic particles may be distinguished from the first metal magnetic particles 31 and the second metal magnetic particles 41 based on the difference in the composition ratio of the elements contained therein. The third metal magnetic particles can fill the gaps between the first metal magnetic particles 31, the gaps between the second metal magnetic particles 41, and the gaps between the first metal magnetic particles 31 and the second metal magnetic particles 41, thereby increasing the mechanical strength of the base 10. Furthermore, the base 10 may include a plurality of fourth metal magnetic particles. The average particle size of the plurality of fourth metal magnetic particles is smaller than the average particle size (third average particle size) of the plurality of third metal magnetic particles.

In at least one embodiment of the present invention, the substrate 10 can contain alumina particles, silica particles, or mixed particles thereof. By containing alumina particles, silica particles, or mixed particles thereof, the linear expansion coefficient of the substrate 10 can be reduced and the mechanical strength can be increased.

In at least one embodiment of the present invention, the first average circularity representing the average circularity of the plurality of first metal magnetic particles 31 is 0.7 or more. In at least one embodiment of the present invention, the second average circularity representing the average circularity of the plurality of second metal magnetic particles 41 is 0.8 or more. The average circularity of the plurality of second metal magnetic particles 41 contained in the base 10 is higher than the average circularity of the plurality of first metal magnetic particles 31 contained in the base 10. In the base 10, the plurality of first metal magnetic particles 31 have a large first average circularity of 0.7 or more, and the plurality of second metal magnetic particles 41 have a second average circularity larger than the first average circularity, so that the stress distortion occurring in the first metal magnetic particles 31 and the second metal magnetic particles 41 is suppressed, and the decrease in the magnetic permeability of the base 10 due to the increase in stress distortion is suppressed.

When the base 10 is produced by compression molding, compressive stress is likely to act on the first metal magnetic particles 31, which have a relatively large diameter. For this reason, large distortion is likely to occur in the first metal magnetic particles 31 during the production of the base 10. The Young's modulus of the metal magnetic particles tends to increase as the Si content ratio increases. Therefore, by making the Si content ratio in the first metal magnetic particles 31 greater than the Si content ratio in the second metal magnetic particles 41, distortion occurring in the first metal magnetic particles 31 can be suppressed.

The second metal magnetic particles 41 have a smaller Si content than the first metal magnetic particles 31, but the second average circularity is larger than the first average circularity, so that the distortion occurring in the second metal magnetic particles 41 is also suppressed. By using a magnetic powder having a higher circularity than the magnetic powder that is the raw material of the first metal magnetic particles 31 as the raw material of the second metal magnetic particles 41, the distortion remaining in the raw material powder of the second metal magnetic particles 41 can be made smaller than the distortion remaining in the raw material powder of the first metal magnetic particles 31. In the compression process during the manufacture of the base 10, the magnetic powder that is the raw material of the second metal magnetic particles 41 is smaller in diameter than the magnetic powder that is the raw material of the first metal magnetic particles 31, so it is less likely to be subjected to molding pressure. Therefore, the second metal magnetic particles 41 (or the raw material powder) is less likely to be distorted even in the compression molding process. In this way, even though the Si content ratio in the second metal magnetic particles 41 is smaller than the Si content ratio in the first metal magnetic particles 31, the occurrence of distortion in the second metal magnetic particles 41 is suppressed.

The second metal magnetic particles 41 have a smaller Si content than the second metal magnetic particles 31, so the Fe content can be increased. Therefore, by including the second metal magnetic particles 41 in the base 10, it is possible to improve the magnetic saturation of the base 10 while suppressing core loss caused by distortion remaining in the metal magnetic particles.

In addition, the higher the circularity of the metal magnetic particles, the smaller the surface area of the metal magnetic particles. When the second average circularity of the second metal magnetic particle group is greater than the first average circularity of the first metal magnetic particle group, the surface area of the second metal magnetic particles can be reduced. This can suppress the aggregation of the second metal magnetic particles 41. When the second metal magnetic particles 41 aggregate, there is a shortage of the second metal magnetic particles 41 that enter the gaps between the first metal magnetic particles 31, and as a result, the filling rate of the metal magnetic particles in the base 1 decreases. Therefore, by making the second average circularity of the second metal magnetic particle group greater than the first average circularity of the first metal magnetic particle group and reducing the surface area of the second metal magnetic particles 41, the aggregation of the second metal magnetic particles 41 can be suppressed, and as a result, the decrease in the filling rate of the metal magnetic particles in the base 10 caused by the aggregation of the second metal magnetic particles 41 can be suppressed.

The average circularity of the first metal magnetic particles 31 in the base 10 can be calculated as follows. First, the base 10 is cut along the T axis (along the coil axis Ax) in the same manner as in the calculation of the average particle size to expose the cross section of the base 10, and an SEM image of the cross section is obtained by photographing the cross section with a scanning electron microscope (SEM) at a magnification of, for example, 500 to 10,000 times, and SEM-EDS mapping is performed within the field of view of this SEM image to identify the first metal magnetic particles 31 and the second metal magnetic particles 41. As described above, the metal magnetic particles contained in the base 10 can be divided into the first metal magnetic particles 31 and the second metal magnetic particles 41 based on whether the content ratio of a specific element (for example, Si) is greater than a predetermined value. Then, the circularity of each of the first metal magnetic particles 31 contained in the SEM image is calculated using commercially available image processing software (for example, Mac-View provided by Mountec Co., Ltd.), and the average value of the calculated circularities is taken as the first average circularity. Similarly, the circularity of each of the second metal magnetic particles 41 contained in the SEM image is calculated, and the average value of the calculated circularities is set as the second average circularity. The magnification when acquiring the SEM image can be changed depending on the particle size of the first metal magnetic particles 31 and/or the second metal magnetic particles 41 to be observed.

In at least one embodiment of the present invention, the first average circularity of the plurality of first metal magnetic particles 31 contained in the base 10 is 0.7 or more, and the second average circularity of the plurality of second metal magnetic particles 41 is both 0.8 or more, so that in the cross section of the base 10, the first metal magnetic particles 31 and the second metal magnetic particles 41 generally have a relatively uncomplicated (i.e., close to a circle) shape as illustrated in FIG. 3. For comparison with the embodiment of the present invention, an example of a cross section of the base of a conventional coil component is shown in FIG. 4. In the conventional coil component, the metal magnetic particles are compressed at a relatively high molding pressure of about 400 MPa to 800 MPa, so that the metal magnetic particles 51 contained in the base of the conventional coil component are deformed during the compression molding process and have a complex shape as shown in FIG. 4. Comparing FIG. 3 and FIG. 4, the outer peripheral surfaces of the first metal magnetic particles 31 and the second metal magnetic particles 41 in the embodiment of the present invention do not have a recess that recesses inward, whereas at least a portion of the metal magnetic particles 51 in the conventional coil component have a recess that recesses inward. Such recesses can also be seen in the photograph submitted as Figure 1 in Patent Document 1.

In at least one embodiment of the present invention, the raw material powder of the metal magnetic particles (for example, the first metal magnetic particles 31 and the second metal magnetic particles 41) contained in the base 10 may be manufactured by an atomization method. The raw material powder of the first metal magnetic particles 31 and the second metal magnetic particles 41 can be manufactured by various gas phase methods, liquid phase methods, or solid phase methods other than the atomization method. In the gas phase method, the raw material gas is heated by a heat source such as a laser or an arc, and the monomers in the raw material gas are condensed to obtain nanoparticles. The gas phase method includes a CVD method, a gas phase synthesis method, and an evaporation and condensation method. As the magnetic powder that is the raw material of the first metal magnetic particles 31 and the second metal magnetic particles 41, it is preferable to use a powder manufactured by a build-up method in which molecular-level raw materials are grown or aggregated by a gas phase method, liquid phase method, or solid phase method, rather than a powder manufactured by a breakdown method in which a lump is crushed. This is because the magnetic powder manufactured by the breakdown method is more likely to generate large stress distortion than the magnetic powder manufactured by the build-up method.

As described above, the base 10 can have a core region 10X and a margin region 10Y. The first average circularity in the core region 10X may be different from the first average circularity in the margin region 10Y. For example, the first average circularity in the core region 10X may be greater than the first average circularity in the margin region 10Y. By making the first average circularity in the core region 10X, where the magnetic flux density of the magnetic flux generated when a current flows through the coil conductor 25, higher than the first average circularity in the margin region 10Y, the magnetic permeability of the base 10 can be further improved. Similarly, in at least one embodiment of the present invention, the second average circularity in the core region 10X may be greater than the second average circularity in the margin region 10Y.

When the first average circularity in the core region 10X and the first average circularity in the margin region 10Y are different, the difference between the two is 5% or less of the first average circularity in the core region 10X. In the base 10, the difference between the first average circularity in the core region 10X and the first average circularity in the margin region 10Y is set within a predetermined range (for example, 5% or less of the first average circularity in the core region 10X), so that the first metal magnetic particles 31 are uniformly distributed in the base 10. Similarly, when the second average circularity in the core region 10X and the second average circularity in the margin region 10Y are different, the difference between the two is 5% or less of the second average circularity in the core region 10X. In the base 10, the difference between the second average circularity in the core region 10X and the second average circularity in the margin region 10Y is within a predetermined range (for example, 5% or less of the second average circularity in the core region 10X), so that the second metal magnetic particles 41 are uniformly distributed in the base 10. By uniformly distributing the first metal magnetic particles 31 and the second metal magnetic particles 41 in the base 10, it is possible to prevent local concentration of magnetic flux in a certain region in the base 10 when a current flows through the coil conductor 25. In addition, by uniformly distributing the first metal magnetic particles 31 and the second metal magnetic particles 41 in the base 10, it is possible to increase the filling rate of the metal magnetic particles in the base 10.

As described above, in at least one embodiment of the present invention, the base 10 can include third metal magnetic particles that are easily deformed according to the surface shape of the first metal magnetic particles 31 and/or the second metal magnetic particles 41. This allows the third metal magnetic particles to effectively improve the mechanical strength of the base 10 by the third metal magnetic particles that have entered between the first metal magnetic particles 31, between the second metal magnetic particles 41, and/or between the first metal magnetic particles 31 and the second metal magnetic particles 41. In this case, the average circularity of the multiple third metal magnetic particles contained in the base 10 (referred to as the "third average circularity" in this specification) is smaller than the second average circularity. As described above, the base 10 can include multiple fourth metal magnetic particles. The average circularity of the multiple fourth metal magnetic particles contained in the base 10 (referred to as the "fourth average circularity" in this specification) is smaller than the third average circularity.

In at least one embodiment of the present invention, the third average circularity may be higher than the second average circularity. In at least one embodiment of the present invention, the third average circularity of the third metal magnetic particles may be 0.8 or more. When the third average circularity is higher than the second average circularity, the surface area of the third metal magnetic particles can be reduced, thereby suppressing aggregation of the third metal magnetic particles. This suppresses a decrease in the filling rate caused by aggregation of the third metal magnetic particles, and the filling rate of the metal magnetic particles in the base 10 can be improved. The base 10 obtained in this manner can increase the magnetic permeability as the filling rate increases.

The Si content in the third metal magnetic particles may be smaller than the Si content in the first metal magnetic particles 31. The third metal magnetic particles may not contain Si. The Fe content in the third metal magnetic particles may be larger than the Fe content in the first metal magnetic particles 31. Thus, by including the third metal magnetic particles in the base 10, the core loss caused by the distortion remaining in the metal magnetic particles can be suppressed, while the magnetic permeability of the base 10 can be improved as the filling rate in the base 10 increases.

The Si content in the fourth metal magnetic particles may be smaller than the Si content in the first metal magnetic particles 31. The fourth metal magnetic particles may not contain Si. The Fe content in the fourth metal magnetic particles may be larger than the Fe content in the first metal magnetic particles 31. Thus, by including the fourth metal magnetic particles in the base 10, it is possible to suppress core loss caused by distortion remaining in the metal magnetic particles, while increasing the filling rate of the base 10 to improve magnetic permeability.

Each of the multiple metal magnetic particles contained in the substrate 10 may be bonded to adjacent metal magnetic particles via an insulating film. The insulating film may contain an oxide of the constituent elements of the metal magnetic particles, or may be formed from an insulating material other than the constituent elements of the metal magnetic particles.

The base 10 may contain a resin. For example, as shown in FIG. 3, the base 10 may contain a resin binder 36 that bonds the metal magnetic particles together. The binder 36 is made of, for example, a thermosetting resin with excellent insulating properties. For example, epoxy resin, polyimide resin, polystyrene (PS) resin, high density polyethylene (HDPE) resin, polyoxymethylene (POM) resin, polycarbonate (PC) resin, polyvinylidene fluoride (PVDF) resin, phenolic resin, polytetrafluoroethylene (PTFE) resin, or polybenzoxazole (PBO) resin may be used as the resin material for the binder 36. In at least one embodiment of the present invention, the content ratio of the resin contained in the base 10 is 1 to 3 wt % when the total mass of the metal magnetic particles contained in the base 10 is 100 wt %.

Next, an example of a manufacturing method for the coil component 1 according to one embodiment of the present invention will be described. An example of a manufacturing method for the coil component 1 using a compression molding method will be described below. The manufacturing method for the coil component 1 using a compression molding method includes a preparation step of kneading metal magnetic particles and resin to produce a mixed resin composition, a compression molding step of compression molding the mixed resin composition to form a molded body, and a heat treatment step of heating the molded body obtained by the compression molding step.

In the preparation step, first, a mixed powder of the first magnetic powder, which is the raw material of the first metal magnetic particles 31, and the second magnetic powder, which is the raw material of the second metal magnetic particles 41, is kneaded with a resin and a diluent solvent to produce a mixed resin composition. When the base also contains a third metal magnetic particle, the mixed powder contains a third magnetic powder, which is the raw material of the third metal magnetic particle. In at least one embodiment of the present invention, particles with an average circularity of 0.9 or more are used as the first magnetic powder, the second magnetic powder, and the third magnetic powder, which are raw materials in the mixed resin composition. The average circularity of the first metal magnetic particles 31, the second metal magnetic particles 41, and the third metal magnetic particles may decrease due to deformation caused by a compression force in the subsequent compression molding step, but may be 0.9 or more in the preparation step.

Next, in the compression molding process, the coil conductor 25 prepared in advance is placed in the molding die, the mixed resin composition produced as described above is placed in the molding die in which the coil conductor 25 is placed, and the mixed resin composition in the molding die is heated and pressurized at an appropriate molding pressure to produce a molded body containing the coil conductor 25 inside. In at least one embodiment of the present invention, the appropriate molding pressure is 100 MPa or less. If the molding pressure is too high, it causes deformation of the metal magnetic particles and reduces the circularity. In an embodiment of the present invention, the molding pressure when producing the molded body can be 50 MPa or less, 40 MPa or less, or 30 MPa or less. If the molding pressure is too low, the filling rate of the metal magnetic particles in the molded body decreases, so a lower limit can be set for the molding pressure. In an embodiment of the present invention, the lower limit of the molding pressure when producing the molded body can be 10 MPa. In this compression molding process, the first magnetic powder is compressed to become the first metal magnetic particles 31, and the second magnetic powder is compressed to become the second metal magnetic particles 41. If the mixed resin composition contains a third magnetic powder, the third magnetic powder is compressed into third metal magnetic particles in the compression molding process.

After the molded body is obtained in the compression molding process, the manufacturing method proceeds to the heat treatment process. In the heat treatment process, the molded body obtained in the compression molding process is heat treated, and the base 10 having the coil conductor 25 provided therein is obtained by this heat treatment. By this heat treatment, the resin in the mixed resin composition hardens to become a binder, and the binder binds the first metal magnetic particles 31 and the second metal magnetic particles 41. The heat treatment in the heat treatment process is performed at a temperature equal to or higher than the hardening temperature of the resin in the mixed resin composition. The heat treatment in the heat treatment process is performed, for example, at 100°C to 200°C for 30 minutes to 240 minutes. The heating temperature in the heat treatment process is 200°C or less. In the formation process of such a base 10, a low molding pressure in the range of 10 to 100 MPa is used. Therefore, high molding pressure does not act on the first metal magnetic particles 31 and the second metal magnetic particles 41, and therefore the stress distortion generated in the first metal magnetic particles 31 and the second metal magnetic particles 41 is suppressed. In addition, since the circularity of the first metal magnetic particles 31 and the second metal magnetic particles 41 is high, the frictional force acting on the first metal magnetic particles 31 and the second metal magnetic particles 41 in the mixed resin composition when compressing the mixed resin composition containing the first metal magnetic particles 31 and the second metal magnetic particles 41 is small, compared to metal magnetic particles with low circularity (or metal magnetic particles whose circularity decreases due to molding pressure). Therefore, the first metal magnetic particles 31 and the second metal magnetic particles 41 are easy to flow in the mixed resin composition during compression molding, so that the first metal magnetic particles 31 and the second metal magnetic particles 41 are easy to take a structure close to a close-packed structure in the molding die. In this way, by increasing the circularity of the first metal magnetic particles 31 and the second metal magnetic particles 41, it is possible to suppress the decrease in the filling rate of the metal magnetic particles in the base 10 caused by using a low molding pressure.

Next, the external electrodes 21 and 22 are formed by applying a conductor paste to both ends of the base 10 obtained as described above. The external electrode 21 is electrically connected to one end of the coil conductor 25 provided in the base 10, and the external electrode 22 is provided so as to be electrically connected to the other end of the coil conductor 25 provided in the base 10. The external electrodes 21 and 22 may include a plating layer. This plating layer may be two or more layers. The two plating layers may include a Ni plating layer and a Sn plating layer provided on the outside of the Ni plating layer. In this manner, the coil component 1 is manufactured.

The manufactured coil component 1 may be mounted on the substrate 2 by a reflow process. In this case, the substrate 2 on which the coil component 1 is arranged passes through a reflow furnace heated to a peak temperature of, for example, 260°C at high speed, and then the external electrodes 21, 22 are solder-joined to the land portion 3 of the mounting substrate 2a, thereby mounting the coil component 1 on the mounting substrate 2 and obtaining the circuit substrate 2.

Next, referring to FIG. 5, a coil component 101 according to another embodiment of the present invention will be described. The coil component 101 is a planar coil. As shown in the figure, the coil component 101 includes a base 110, an insulating plate 150 provided within the base 110, a coil conductor 125 provided on the upper surface of the insulating plate 150 within the base 110, an external electrode 121 provided on the base 110, and an external electrode 122 provided on the base 110 at a distance from the external electrode 121. The base 110 is formed from the same magnetic material as the base 10. The insulating plate 150 is a member formed into a plate shape from an insulating material.

The base 110 is made of a magnetic material containing a plurality of metal magnetic particles, similar to the base 10. In one embodiment, the base 110 contains a plurality of first metal magnetic particles 31 and a plurality of second metal magnetic particles 41. In the base 110, the first average circularity representing the average circularity of the plurality of first metal magnetic particles 31 is 0.7 or more, and the second average circularity representing the average circularity of the plurality of second metal magnetic particles 41 is 0.8 or more. The average circularity of the plurality of second metal magnetic particles 41 contained in the base 110 is higher than the average circularity of the plurality of first metal magnetic particles 31 contained in the base 10. The base 110 has a roughly rectangular parallelepiped shape. The description of the base 10 also applies to the base 110 as much as possible.

In the illustrated embodiment, the coil conductor 125 has a turn portion wound in a spiral shape around the coil axis Ax extending along the thickness direction (T direction) on the upper surface of the insulating plate 150. The coil conductor 125 is connected to the external electrode 121 at one end and to the external electrode 122 at the other end. The coil conductor 125 may have a shape other than the shape shown in the figure. For example, the coil conductor 125 may have a turn portion wound in a spiral shape around the coil axis Ax on each of the upper and lower surfaces of the insulating plate 150. In this case, the coil conductor 125 has a connection portion that connects the turn portion provided on the upper surface of the insulating plate 150 and the turn portion provided on the lower surface of the insulating plate 150. The coil conductor 125 may have any shape other than the shapes specifically described in this specification, as long as it does not cause a contradiction.

Next, an example of a method for manufacturing the coil component 101 will be described. First, an insulating plate formed into a plate shape from a magnetic material is prepared. Next, photoresist is applied to the upper and lower surfaces of the insulating plate, and then a conductor pattern is exposed and transferred to each of the upper and lower surfaces of the insulating plate, followed by a development process. As a result, a resist having an opening pattern for forming the coil conductor 125 is formed on each of the upper and lower surfaces of the insulating plate 150.

Next, each of the opening patterns is filled with a conductive metal by plating. Then, the resist is removed from the insulating plate 150 by etching, so that the coil conductors 125 are formed on the upper and lower surfaces of the insulating plate. In addition, the through holes provided in the insulating plate 150 are filled with a conductive metal, so that vias are formed that connect the front and back sides of the insulating plate to the coil conductors 125.

Next, the base 110 is formed on both sides of the insulating plate 150 on which the coil conductor 125 is formed. A compression molding process is performed to form the base 110. In this compression molding process, first, a mixed powder of the first magnetic powder, which is the raw material of the first metal magnetic particles 31, and the second magnetic powder, which is the raw material of the second metal magnetic particles 41, is kneaded with resin and a diluent solvent to obtain a mixed resin composition. Next, this mixed resin composition is applied in a sheet form on a substrate such as a PET film, and the applied mixed resin composition is dried to volatilize the diluent solvent. This produces a sheet-like molded body in which a plurality of first metal magnetic particles 31 and a plurality of second metal magnetic particles 41 are dispersed in the resin. This sheet-like resin molded body is called a magnetic sheet. Two magnetic sheets are prepared, the coil conductor 125 is placed between the two magnetic sheets, and the coil conductor is heated and pressurized at 10 to 100 MPa to produce a compression molded body (laminate) containing the coil conductor inside.

The manufacturing method of the coil component 101 then proceeds to a heat treatment step. In the heat treatment step, the laminate is heat treated to obtain a base 110 having a coil conductor 125 therein. This heat treatment hardens the resin in the mixed resin composition to become a binder, and the binder bonds the first metal magnetic particles 31 and the second metal magnetic particles 41 together. The heat treatment in the heat treatment step is performed at a temperature equal to or higher than the hardening temperature of the resin in the mixed resin composition. The heat treatment in the heat treatment step is performed, for example, at 100°C to 200°C for 30 to 240 minutes.

Another example of the method for producing the laminate in the above manufacturing process will be described. In this method for producing the laminate, the insulating plate 150 on which the coil conductor 125 is formed is placed in a molding die, and a mixed resin composition obtained by kneading a mixed powder of the first magnetic powder and the second magnetic powder with a resin and a dilution solvent is placed in the molding die, and a molding pressure of 10 to 100 MPa is applied while heating to produce a molded body having the coil conductor 125 inside. The above-mentioned heat treatment is performed on this molded body to obtain the base body 110 having the coil conductor 125 inside.

Next, a conductive paste is applied to both ends of the base 110 obtained as described above to form the external electrodes 121 and 122. The external electrode 121 is electrically connected to one end of the coil conductor 125 provided in the base 110, and the external electrode 122 is provided so as to be electrically connected to the other end of the coil conductor 125 provided in the base 110. In this manner, the coil component 101 is manufactured.

Next, referring to FIG. 6, a coil component 201 according to another embodiment of the present invention will be described. The coil component 201 is a laminated coil. As shown in the figure, the coil component 201 includes a base 210, a coil conductor 225 provided within the base 210, an external electrode 221 provided on the base 210, and an external electrode 222 provided on the base 210 at a distance from the external electrode 221. The base 210 is made of a magnetic material, similar to the base 10.

The base 210 is made of a magnetic material containing a plurality of metal magnetic particles, similar to the base 10. The base 210 in at least one embodiment of the present invention contains a plurality of first metal magnetic particles 31 and a plurality of second metal magnetic particles 41. In the base 210, the first average circularity representing the average circularity of the plurality of first metal magnetic particles 31 is 0.7 or more, and the second average circularity representing the average circularity of the plurality of second metal magnetic particles 41 is 0.8 or more. The average circularity of the plurality of second metal magnetic particles 41 contained in the base 110 is higher than the average circularity of the plurality of first metal magnetic particles 31 contained in the base 10. The base 210 has a roughly rectangular parallelepiped shape. The description of the base 10 also applies to the base 210 as much as possible.

The coil conductor 225 is wound in a spiral shape around a coil axis Ax extending along the thickness direction (T-axis direction). The coil conductor 225 has conductor patterns C11 to C16 and via conductors (not shown) that connect adjacent conductor patterns C11 to C16. The via conductors extend roughly along the coil axis Ax. The conductor patterns C11 to C16 are formed, for example, by printing a conductive paste made of a metal or alloy with excellent conductivity on a sheet-shaped compression molded body by a screen printing method. The conductive paste may be made of Ag, Pd, Cu, Al, or an alloy thereof. Each of the conductor patterns C11 to C16 is electrically connected to the adjacent conductor pattern via the via conductor. The conductor patterns C11 to C16 connected in this way form the spiral coil conductor 225.

Next, an example of a method for manufacturing the coil component 201 will be described. The coil component 201 can be manufactured, for example, by a lamination process. An example of a method for manufacturing the coil component 201 by a lamination process will be described below.

First, a plurality of magnetic sheets made of a magnetic material are prepared. Each of these magnetic sheets is obtained by kneading a mixed powder of the first magnetic powder and the second magnetic powder with a heat-decomposable resin (e.g., polyvinyl butyrate (PVB) resin) as a binder and a diluting solvent to obtain a mixed resin composition, which is applied in a sheet form on a substrate such as a PET film, and drying the applied mixed resin composition to volatilize the diluting solvent. This produces a magnetic sheet in which the first magnetic powder, which is the raw material for the first metal magnetic particles 31, and the second magnetic powder, which is the raw material for the second metal magnetic particles 41, are dispersed in the resin. The magnetic sheet thus produced is placed in a mold and pressurized at 10 to 100 MPa while being heated, to produce a sheet-shaped compression molded body. This pressure treatment causes the first magnetic powder to be compressed into the first metal magnetic particles 31, and the second magnetic powder to be compressed into the second metal magnetic particles 41.

Next, coil conductors are provided on the sheet-shaped compression molded body as follows. First, through holes are formed in the sheet-shaped compression molded body at predetermined positions in the sheet-shaped compression molded body, penetrating the sheet-shaped compression molded body in the T-axis direction. Next, conductive paste is printed on the upper surface of each sheet-shaped compression molded body by screen printing to form an unsintered conductor pattern on each compression molded body, and the conductive paste is embedded in each through hole formed in each compression molded body.

Next, the compression molded bodies are stacked to obtain a coil laminate. The compression molded bodies are stacked so that adjacent unsintered conductor patterns corresponding to the conductor patterns C11 to C16 formed on each magnetic sheet are electrically connected to each other through unsintered vias.

Next, multiple sheet-like compression molded bodies are stacked to form an upper laminate that will become the upper cover layer. Also, multiple sheet-like compression molded bodies are stacked to form a lower laminate that will become the lower cover layer. Next, the lower laminate, coil laminate, and upper laminate are stacked in this order from the negative side to the positive side of the T-axis direction, and each of these stacked laminates is thermocompressed by a press to obtain a main laminate. The main laminate may also be formed by stacking all of the prepared sheet-like compression molded bodies in order and thermocompressing the stacked compression molded bodies together, without forming the lower laminate, coil laminate, and upper laminate.

Then, the main body stack is diced into pieces of the desired size using a cutting machine such as a dicing machine or laser processing machine, to obtain a chip stack. Next, this chip stack is subjected to a heat treatment. This heat treatment is performed, for example, at 100°C to 200°C for 30 to 240 minutes. If necessary, the ends of this chip stack are subjected to a polishing process such as barrel polishing.

Next, conductive paste is applied to both ends of the chip stack to form external electrodes 221 and 222. This completes the coil component 201.

Next, referring to FIG. 7, a coil component 301 according to another embodiment of the present invention will be described. The coil component 301 according to one embodiment of the present invention is a wound inductor. As shown in the figure, the coil component 301 includes a base 310, a coil conductor 325 (winding 325), a first external electrode 321, and a second external electrode 322. The base 310 includes a winding core 311, a rectangular parallelepiped flange 312a provided at one end of the winding core 311, and a rectangular parallelepiped flange 312b provided at the other end of the winding core 311. The coil conductor 325 is wound around the winding core 311. The coil conductor 325 includes a conductor made of a metal material having excellent electrical conductivity and an insulating coating that covers the conductor. The first external electrode 321 is provided along the lower surface of the flange 312a, and the second external electrode 322 is provided along the lower surface of the flange 312b.

The base 310 is made of a magnetic material containing a plurality of metal magnetic particles, similar to the base 10. In one embodiment, the base 310 contains a plurality of first metal magnetic particles 31 and a plurality of second metal magnetic particles 41. In the base 310, the first average circularity representing the average circularity of the plurality of first metal magnetic particles 31 is 0.7 or more, and the second average circularity representing the average circularity of the plurality of second metal magnetic particles 41 is 0.8 or more. The average circularity of the plurality of second metal magnetic particles 41 contained in the base 310 is higher than the average circularity of the plurality of first metal magnetic particles 31 contained in the base 10. The explanation regarding the base 10 also applies to the base 310 as much as possible.

Next, an example of a method for manufacturing the coil component 301 will be described. First, the base 310 is produced. The base 310 includes a preparation step of preparing a mixed resin composition and a compression molding step of compression molding the mixed resin composition. In the preparation step, first, a mixed powder of the first magnetic powder and the second magnetic powder is kneaded with a resin and a dilution solvent to obtain a mixed resin composition. Metal magnetic particles are dispersed in this mixed resin composition. This mixed resin composition is placed in a molding die, and the mixed resin composition in the molding die is heated and pressurized at a molding pressure of 10 to 100 MPa to produce a molded body. By this pressure treatment, the first magnetic powder is compressed into the first metal magnetic particles 31, and the second magnetic powder is compressed into the second metal magnetic particles 41.

Next, a heat treatment process is carried out to heat the molded body obtained by the compression molding process. This heat treatment process results in a base body 310. This heat treatment hardens the resin in the mixed resin composition to become a binder, and the binder bonds the first metal magnetic particles 31 and the second metal magnetic particles 41 together. The heat treatment is carried out, for example, at 100°C to 200°C for 30 to 240 minutes.

Next, a coil installation process is performed in which a coil conductor 325 is provided on the base body 310 obtained by the above heat treatment process. In the coil installation process, the coil conductor 325 is wound around the base body 310, and one end of the coil conductor 325 is connected to the first external electrode 321 and the other end is connected to the second external electrode 322. In this manner, the coil component 301 is obtained.

Next, with reference to Figures 8a and 8b, another embodiment of the method for manufacturing the coil component 1 will be described. First, in step S11, a base 10 containing a coil conductor 25 therein is produced. As shown in Figure 10b, the base 10 produced by this method has a main body 11, a protruding portion 12 protruding downward (in the negative direction of the T-axis) from the main body 11, and a plate core 20 provided below the main body 11 and radially inward of the protruding portion 11. The plate core 20 is not shown in Figures 1 and 2.

Figure 8b is a diagram showing substeps included in step S11 of producing the base body 10, and is a flow diagram showing an example of a manufacturing process of a molded body, which is a precursor of the base body 10, by a compression molding method. Figures 9a, 9b, 10a, and 10b each show a schematic diagram of a part of the manufacturing process of the base body 10. In the example shown in Figures 9a to 10b, the base body 10 has a main body portion 11, a protrusion portion 11, and a plate core 20. Specifically, Figures 9a and 9b show the process of producing the plate core 20, and Figures 10a and 10b show the process of producing the main body portion 11 and the protrusion portion 12 that include the coil conductor 25 therein.

To manufacture the base body 10, first, in step S11A, a magnetic material 60 for producing a precursor of the plate core 20 (precursor 120 shown in FIG. 9b) is prepared. The magnetic material 60 is produced by kneading a mixed powder obtained by mixing a relatively large-diameter first magnetic powder and a relatively small-diameter second magnetic powder with a resin and a diluting solvent. The first magnetic powder and the second magnetic powder become the first metal magnetic particles 31 and the second metal magnetic particles 41, respectively, in the finished coil component 1. Both the first magnetic powder and the second magnetic powder have a high degree of circularity. The circularity of the first magnetic powder and the second magnetic powder is, for example, 0.9 or more. The average particle size of the first magnetic powder is larger than the average particle size of the second magnetic powder. A thermosetting resin can be used as the resin for the magnetic material 60. As the thermosetting resin, polyvinyl butyral (PVB) resin, epoxy resin, silicone resin, or other known resin materials can be used. The magnetic material 60 may be a mixed powder with a magnetic powder other than the first magnetic powder and the second magnetic powder (for example, at least one of the third magnetic powder and the fourth magnetic powder). The magnetic material 60 may include at least one of alumina particles and silica particles.

Next, in step S11B, as shown in FIG. 9a, the magnetic material 60 is put into the cavity of the die 51a and primary molding is performed to obtain a precursor 120. Specifically, after the magnetic material 60 is put into the cavity, the punch 52a is moved downward along the stroke direction along the T-axis direction to compress the magnetic material 60 with a first molding pressure. The die 51a and punch 52a shown in FIG. 9a are exemplary, and the mold used for primary molding is not limited to the die 51a and punch 52a shown in FIG. 9a. For example, the die 51a may be open on the positive side and the negative side in the T-axis direction (i.e., the upper side and the lower side of the paper). In this case, the punch 52a may be a pair of punches that face each other in the T-axis direction and move along the T-axis direction. The first molding pressure can be set in the range of 10 to 100 MPa. By compressing the magnetic material 60 in this way, a precursor 120 of the plate core 20 is produced as shown in FIG. 9b.

Next, in step S11C, magnetic material 70 to be used in the subsequent secondary molding is prepared. Magnetic material 70 may be the same as magnetic material 60.

Subsequently, in step S11D, the precursor 120 and the magnetic material 70 produced in step S11A are subjected to secondary molding to obtain a molded body that is a precursor of the base body 10. Specifically, as shown in FIG. 10a, the precursor 120 of the plate core 20 is placed in the cavity of a die 51b that is separate from the die 51a. When viewed from the stroke direction (T-axis direction), the cavity of the die 51b has a larger area than the precursor 120 of the plate core 20. For example, the dimensions of the cavity of the die 51b in the L-axis direction and the W-axis direction are larger than the corresponding dimensions of the die 51a. Therefore, when the precursor 120 is placed in the cavity of the die 51b, a gap G is generated between the precursor 120 and the side wall of the die 51b that defines the cavity. The precursor 120 may be arranged so that the gap G between the outer edge of the precursor 120 and the side wall of the die 51b has a uniform dimension when viewed from the stroke direction (T-axis direction).

Next, the coil conductor 25, which has been prepared in advance, is placed on the precursor 120. The coil conductor 25 is placed in the die cavity so that the coil axis Ax coincides or nearly coincides with the stroke direction of the punch 51b. If the angle between the coil axis and the stroke direction of the punch is within 30 degrees, it can be determined that the coil axis Ax and the stroke direction are nearly coincident.

Next, magnetic material 70 is placed in the cavity of die 51b in which precursor 120 and coil conductor 25 are placed. Gap G between the outer edge of precursor 120 and the sidewall of die 51b may be filled with magnetic material 70. If the size of gap G is small, gap G does not need to be filled with magnetic material 70.

After the magnetic material 70 is placed in the cavity, the punch 52b is moved downward along the stroke direction to compress the precursor 120 and the magnetic material 70 in the cavity with a second molding pressure. The second molding pressure is lower than the first molding pressure. The second molding pressure can be set, for example, in the range of 10 to 100 MPa.

After the pressurization in the secondary molding, the die 51b may be heated so that the inside of the cavity of the die 51b is at or above the curing temperature of the first thermosetting resin contained in the magnetic material 60 and the second thermosetting resin contained in the magnetic material 70. In other words, the heating process in step S12 can be performed consecutively with the secondary molding process in step S11D. This heating process causes the precursor 120 to become the plate core 20, and the molded and pressurized magnetic material 70 to become the main body 11 and the protrusions 12.

By making the width of the gap G uniform when viewed from the stroke direction (T-axis direction), the width of the protrusion 12 formed as described above can be made uniform. In other words, the protrusion 12 can be formed between the plate core 20 and each of the first end face 10c, the second end face 10d, the first side face 10e, and the second side face 10f of the base 10 so as to extend in the circumferential direction around the coil axis Ax along these four faces, and the dimensions of the protrusion 12 in the radial direction centered on the coil axis Ax can be made uniform. In order to make the protrusion 12 uniform, the shape of the precursor 120 of the plate core 20 is preferably a rectangular parallelepiped shape when the base 10 is rectangular parallelepiped, but is not limited to this and may be, for example, a cylindrical shape, an elliptical cylindrical shape, or other shapes symmetrical with respect to the coil axis Ax.

If the gap G is not filled with the magnetic material 70, the precursor 120 is stretched in a direction perpendicular to the T axis by the pressure applied in the secondary molding. In this case, the gap G that existed between the precursor 120 and the side wall of the cavity of the die 51b before the pressure applied in the secondary molding is filled with the plate core 20 formed from the precursor 120. A portion of the gap G may be filled with the magnetic material 70, and the remainder may not be filled with the magnetic material 70. In this case, the protrusion 12 is formed in the area of the gap G filled with the magnetic material 70, and a portion of the plate core 20 formed by stretching the precursor 120 is placed in the remaining portion.

By applying pressure during the primary and secondary molding, the first magnetic powder and the second magnetic powder contained in the magnetic material 60 are compressed to become the first metal magnetic particles 31 and the second metal magnetic particles 41, respectively.

The secondary molding may be performed using the same die 51a and punch 52a as in the primary molding. In this case, the base 10 does not include the protrusion 12.

Next, in step S13, the external electrodes 21 and 22 are formed by applying a conductor paste to the surface of the base 10 obtained in step S12. The external electrode 21 is electrically connected to one end of the coil conductor 25 provided in the base 10, and the external electrode 22 is provided so as to be electrically connected to the other end of the coil conductor 25 provided in the base 10. The external electrodes 21 and 22 may include a plating layer. This plating layer may be two or more layers. The two plating layers may include a Ni plating layer and a Sn plating layer provided on the outside of the Ni plating layer. The coil conductor 25 may be arranged so that the end of the coil conductor 25 is exposed to the outside from the base 10, and the part of the coil conductor 25 exposed from the magnetic base 10 is bent toward the bottom surface 10b, so that the part of the coil conductor 25 exposed to the outside from the base 10 may be used as an external electrode.

In this way, the coil component 1 is manufactured. The manufactured coil component 1 may be mounted on the mounting substrate 2a by a reflow process. In this case, the substrate 2 on which the coil component 1 is arranged passes through a reflow furnace heated to a peak temperature of, for example, 260°C at high speed, and then the external electrodes 21, 22 are solder-joined to the land portion 3 of the mounting substrate 2a, thereby mounting the coil component 1 on the mounting substrate 2a and obtaining the circuit substrate 2.

Eight types of coil components were created as follows. The coil components are called samples 1 to 8, respectively. To create the coil components of samples 1 to 10, first, a first magnetic powder with an average particle size of 20 μm and a second magnetic powder with an average particle size of 4 μm were prepared. The first magnetic powder is a raw material powder of the first metal magnetic particles 31, and the second magnetic powder is a raw material powder of the second metal magnetic particles 41. The average circularity of the first magnetic powder was approximately 0.8, and the average circularity of the second magnetic powder was approximately 0.9. Ten samples were taken from the metal magnetic particles before mixing, and the average circularity of each of the ten samples was taken as the average value. The average particle size was taken from ten samples taken from the metal magnetic particles before mixing, and the average particle size of the ten samples was taken as the average value. The first metal magnetic particles 31 (first magnetic powder) and the second metal magnetic particles 41 (second magnetic powder) were made of an Fe-Si-Cr crystalline alloy. The Si content ratios in samples 1 to 10 were as shown in Table 1.

The first and second magnetic powders were mixed in a ratio of 70 wt% first magnetic powder and 30 wt% second magnetic powder to obtain mixed powders for each sample.

Next, the mixed powder for each sample was kneaded with epoxy resin to produce a mixed resin composition. Next, a pre-prepared copper winding coil with an insulating film on the surface was placed in a molding die, and the mixed resin composition produced as described above was placed in the molding die in which the winding coil was placed, and a molding pressure of 30 MPa was applied to the mixed resin composition in the molding die to produce a molded body containing a coil conductor inside. This pressure compresses the first magnetic powder and the second magnetic powder, and they become the first metal magnetic particles 31 and the second metal magnetic particles 41, respectively. Next, the molded body produced as described above was heat-treated at 180°C for 120 minutes to harden the resin in the mixed resin composition. This resulted in a base body having a coil conductor inside.

Next, a conductive paste was applied to both ends of the substrate obtained as described above to form external electrodes 21 and 22. The coil components obtained in this manner were designated as samples 1 to 8.

For each of the samples 1 to 8 obtained as described above, the inductance (μH) and the Q value at a frequency of 1 MHz were measured using a commercially available impedance analyzer.

The average circularity of the large particles and the average circularity of the small particles contained in each of Samples 1 to 8 were calculated as follows. Each of the coil components of Samples 1 to 5 was cut along the coil axis of the winding coil to expose the cross section of the base, and multiple SEM images of the cross section were taken with a scanning electron microscope (SEM) at a magnification of 2000 times. The magnification for taking the SEM to calculate the circularity can be determined according to the particle size of the metal magnetic particles to be measured. For example, when the particle size is 1 μm to 30 μm, the image is taken at a magnification of 2000 times, when the particle size is smaller than 1 μm, the image is taken at a magnification of about 10,000 times, and when the particle size is larger than 30 μm, the image is taken at a magnification of about 500 times. In this way, by adjusting the magnification according to the particle size of the metal magnetic particles to be measured, the particle size of the metal magnetic particles relative to the size of the observation area can be leveled. SEM-EDS mapping was performed within the field of view of each of the multiple SEM images obtained as described above to identify the first metal magnetic particles 31 and the second metal magnetic particles 41. The SEM image was then analyzed using Mac-View provided by Mountec Co., Ltd., the circularity of each of the first metal magnetic particles 31 contained in the SEM image was calculated, and the average value of the calculated circularities was taken as the first average circularity. Similarly, the SEM image was analyzed using Mac-View, the circularity of each of the second metal magnetic particles 41 contained in the SEM image was calculated, and the average value of the calculated circularities was taken as the second average circularity.

The above measurement results and calculation results are shown in Table 2 below.

From the measurement results shown in Table 2, it was confirmed that in each of the samples 1 to 6 (Examples 1 to 6), a superior inductance and Q value were obtained compared to Samples 7 to 8 (Comparative Examples 1 to 2). In Samples 1 to 6, the content ratio of Si in the first metal magnetic particles 31 is greater than the content ratio of Si in the second metal magnetic particles 41, so that the Young's modulus of the first metal magnetic particles 31, which is susceptible to stress in the compression molding process, can be made greater than the Young's modulus of the second metal magnetic particles 41, which is considered to have suppressed the distortion occurring in the first metal magnetic particles 31. In addition, in Samples 1 to 6, the second average circularity of the second metal magnetic particles 41 is greater than the first average circularity of the first metal magnetic particles 31, so that it is considered that a large stress did not act on the second metal magnetic particles 41 (or the second magnetic powder, which is the raw material powder thereof) in the compression molding process. In this way, by reducing the stress acting on the second metal magnetic particles 41 in the compression molding process, the distortion occurring in the second metal magnetic particles 41 can be suppressed.

On the other hand, in sample 7, the second average circularity of the second metal magnetic particles 41 is reduced to 0.7, so it is believed that a large stress acts on the second metal magnetic particles 41 (or the second magnetic powder, which is the raw material powder) in the compression molding process, and this large stress causes a large distortion in the second metal magnetic particles 41. Also, in sample 8, the Si content in the first metal magnetic particles 31 is smaller than the Si content in the second metal magnetic particles 41, so it is believed that a large stress acts on the first metal magnetic particles 31 (or the first magnetic powder, which is the raw material) in the compression molding process, and this large stress causes a large distortion in the first metal magnetic particles 31.

Next, the effects of the above embodiment will be described. According to at least one embodiment of the present invention, since the content ratio of Si in the first metal magnetic particle 31 is greater than the content ratio of Si in the second metal magnetic particle 41, the distortion occurring in the first metal magnetic particle 31 can be suppressed. In addition, since the second average circularity of the second metal magnetic particle 41 is greater than the first average circularity of the first metal magnetic particle 31, a large stress is not applied to the second metal magnetic particle 41 during the production of the second magnetic powder, which is the raw material powder, or during the process of compressing the second magnetic powder to obtain the second metal magnetic particle 41. Therefore, no large distortion occurs in the second metal magnetic particle 41. This makes it possible to suppress the decrease in magnetic permeability and core loss of the base 10 caused by stress distortion occurring in the metal magnetic particle. In addition, by increasing the first average circularity of the first metal magnetic particle group and the second average circularity of the second metal magnetic particle group, the contact area between the metal magnetic particles contained in the first metal magnetic particle group and the second metal magnetic particle group can be reduced, making it difficult for insulation breakdown to occur between the metal magnetic particles. Therefore, in this embodiment of the present invention, the resistivity of the substrate 10 can be increased.

According to at least one embodiment of the present invention, the base 10 includes a first group of metal magnetic particles having a first average particle size and a second group of metal magnetic particles having a second average particle size smaller than the first average particle size, so that the second metal magnetic particles penetrate between the first metal magnetic particles, thereby increasing the filling rate of the metal magnetic particles in the base 10.

According to at least one embodiment of the present invention, the first metal magnetic particle group has a first average circularity of 0.7 or more, and the second metal magnetic particle group has a second average circularity larger than the first average circularity, so that the first metal magnetic particles and the second metal magnetic particles have small surface areas according to their respective circularities. Since the first metal magnetic particles and the second metal magnetic particles have small surface areas according to their respective circularities, the aggregation of the metal magnetic particles can be suppressed in the base 10, and as a result, the decrease in the filling rate of the metal magnetic particles due to the aggregation of the metal magnetic particles can be suppressed. According to at least one embodiment of the present invention, since the smaller diameter second metal magnetic particles have a higher circularity than the larger diameter first metal magnetic particles, it is possible to suppress the aggregation of the second metal magnetic particles, which are more likely to aggregate than the first metal magnetic particles. By making the first average circularity of the first metal magnetic particle group 0.8 or more, the aggregation of the first metal magnetic particles 31 can be further suppressed.

According to at least one embodiment of the present invention, the weight ratio of the multiple large-diameter first metal magnetic particles 31 in the base 10 is at least twice the weight ratio of the multiple small-diameter second metal magnetic particles 41, thereby further increasing the magnetic permeability of the base 10.

According to at least one embodiment of the present invention, by containing Si in the first metal magnetic particle 31 and the second metal magnetic particle 41, the crystal magnetic anisotropy constant and the magnetostriction constant of the first metal magnetic particle 31 and the second metal magnetic particle 41 can be reduced, and the coercive force of the first metal magnetic particle 31 and the second metal magnetic particle 41 can be reduced, so that the hysteresis loss can be reduced. In addition, by containing Si in the first metal magnetic particle 31 and the second metal magnetic particle 41, the electrical resistivity of the first metal magnetic particle 31 and the second metal magnetic particle 41 can be increased, and thus the eddy current loss in the first metal magnetic particle 31 can be reduced. Since the content ratio of Si in the first metal magnetic particle 31 is high, and the content ratio of Si in the second metal magnetic particle 41 is also high, the eddy current loss in the large-diameter first metal magnetic particle 31 in which eddy currents are likely to occur can be effectively suppressed.

According to at least one embodiment of the present invention, the average circularity of the first metal magnetic particles 31 contained in the core region 10X, where the magnetic flux density of the magnetic flux generated when a current flows through the coil conductor 25, is higher, is smaller than the average circularity of the first metal magnetic particles 31 contained in the margin region 10Y, so that the magnetic permeability of the base 10 can be further increased.

According to at least one embodiment of the present invention, the third metal magnetic particles can fill the gaps between the first metal magnetic particles, between the second metal magnetic particles, and between the first metal magnetic particles and the second metal magnetic particles, thereby increasing the mechanical strength of the substrate.

According to at least one embodiment of the present invention, the third metal magnetic particles can fill more of the gaps between the first metal magnetic particles, between the second metal magnetic particles, and between the first metal magnetic particles and the second metal magnetic particles, thereby increasing the filling rate of the metal magnetic particles in the base 10.

The dimensions, materials, and arrangements of each component described in the various embodiments above are not limited to those explicitly described in each embodiment, and each component can be modified to have any dimensions, materials, and arrangements that may fall within the scope of the present invention.

Components not explicitly described in this specification may be added to each of the above-described embodiments, and some of the components described in each embodiment may be omitted.

The designations "first," "second," "third," and the like in this specification are used to identify components and do not necessarily limit the number, order, or content. Furthermore, numbers for identifying components are used in different contexts, and a number used in one context does not necessarily indicate the same configuration in another context. Furthermore, this does not prevent a component identified by a certain number from also serving the function of a component identified by another number.

This specification also discloses the following techniques.
[Appendix 1]
a base including: a first metal magnetic particle group consisting of a plurality of first metal magnetic particles each containing Fe and Si and having a first average circularity; a second metal magnetic particle group consisting of a plurality of second metal magnetic particles each containing Fe and Si and having a second average circularity larger than the first average circularity; and a resin binder;
A coil conductor provided on the substrate;
a first external electrode electrically connected to the coil conductor;
a second external electrode electrically connected to the coil conductor;
Equipped with
A coil component, wherein a Si content in each of the plurality of first metal magnetic particles is higher than a Si content in each of the plurality of second metal magnetic particles.
[Appendix 2]
The first average circularity is 0.8 or more.
2. The coil component according to claim 1.
[Appendix 3]
In the base, a weight ratio of the plurality of first metal magnetic particles is greater than a weight ratio of the plurality of second metal magnetic particles.
3. The coil component according to claim 1 or 2.
[Appendix 4]
a first average particle size representing the average particle size of the first metal magnetic particle group is at least twice as large as a second average particle size representing the average particle size of the second metal magnetic particle group;
4. The coil component according to claim 1 ,
[Appendix 5]
the substrate includes a third metal magnetic particle group consisting of a plurality of third metal magnetic particles each containing Fe and Si and having a third average circularity smaller than the second average circularity;
5. The coil component according to claim 1 ,
[Appendix 6]
A coil component according to any one of Supplementary Note 1 to Supplementary Note 5;
a mounting substrate joined to the external electrodes by solder;
A circuit board comprising:
[Appendix 7]
7. An electronic device comprising the circuit board according to claim 6.
[Appendix 8]
a substrate fabrication step of fabricating a substrate including a coil conductor extending around a coil axis therein;
an external electrode preparation step of providing an external electrode on the base;
Equipped with
the base includes a first metal magnetic particle group consisting of a plurality of first metal magnetic particles each containing Fe and Si and having a first average circularity of 0.8 or more, a second metal magnetic particle group consisting of a plurality of second metal magnetic particles each containing Fe and Si and having a second average circularity larger than the first average circularity, and a resin binder;
a content ratio of Si in each of the plurality of first metal magnetic particles is higher than a content ratio of Si in each of the plurality of second metal magnetic particles;
A manufacturing method for coil components.
[Appendix 9]
The substrate preparation step includes:
a first molding step of forming a first molded part by applying a first molding pressure to a first magnetic material including a first magnetic powder, a second magnetic powder having an average circularity larger than that of the first magnetic powder, and a first thermosetting resin;
a second molding step of covering the coil conductor provided in the first molding part and applying a second molding pressure smaller than the first molding pressure to a second magnetic material including the first magnetic powder, the second magnetic powder, and a second thermosetting resin to form a magnetic base including the first molding part;
9. The method for manufacturing a coil component according to claim 8, comprising:
[Appendix 10]
The first molding pressure is 10 MPa or more and 100 MPa or less.
A method for manufacturing the coil component according to claim 9.
[Appendix 11]
The second molding pressure is 10 MPa or more and 100 MPa or less.
A method for manufacturing a coil component according to claim 9 or 10.
[Appendix 12]
The method further includes a heating step of heating the base at a heating temperature that is equal to or higher than a thermosetting temperature of the first thermosetting resin and equal to or higher than a thermosetting temperature of the second thermosetting resin.
12. A method for manufacturing a coil component according to any one of claims 8 to 11.
[Appendix 13]
The heating temperature is lower than 200° C.
A method for manufacturing the coil component according to claim 12.

REFERENCE SIGNS LIST 1, 101, 201, 301 Coil component 10, 110, 210, 310 Base 21, 22, 121, 122, 221, 222, 321, 322 External electrode 25, 125, 225, 325 Coil conductor 31 First metal magnetic particle 41 Second metal magnetic particle 10X Core region 10Y Margin region Ax Coil axis

Claims (13)

a base including: a first metal magnetic particle group consisting of a plurality of first metal magnetic particles each containing Fe and Si and having a first average circularity; a second metal magnetic particle group consisting of a plurality of second metal magnetic particles each containing Fe and Si and having a second average circularity larger than the first average circularity; and a resin binder;
A coil conductor provided on the substrate;
a first external electrode electrically connected to the coil conductor;
a second external electrode electrically connected to the coil conductor;
Equipped with
A coil component, wherein a Si content in each of the plurality of first metal magnetic particles is higher than a Si content in each of the plurality of second metal magnetic particles. The first average circularity is 0.8 or more.
The coil component according to claim 1 . In the base, a weight ratio of the plurality of first metal magnetic particles is greater than a weight ratio of the plurality of second metal magnetic particles.
The coil component according to claim 1 or 2. a first average particle size representing the average particle size of the first metal magnetic particle group is at least twice as large as a second average particle size representing the average particle size of the second metal magnetic particle group;
The coil component according to claim 1 or 2. the substrate includes a third metal magnetic particle group consisting of a plurality of third metal magnetic particles each containing Fe and Si and having a third average circularity smaller than the second average circularity;
The coil component according to claim 1 or 2. The coil component according to claim 1 or 2;
a mounting substrate joined to the external electrodes by solder;
A circuit board comprising: An electronic device comprising the circuit board according to claim 6. a substrate fabrication step of fabricating a substrate including a coil conductor extending around a coil axis therein;
an external electrode preparation step of providing an external electrode on the base;
Equipped with
the base includes a first metal magnetic particle group consisting of a plurality of first metal magnetic particles each containing Fe and Si and having a first average circularity of 0.8 or more, a second metal magnetic particle group consisting of a plurality of second metal magnetic particles each containing Fe and Si and having a second average circularity larger than the first average circularity, and a resin binder;
a content ratio of Si in each of the plurality of first metal magnetic particles is higher than a content ratio of Si in each of the plurality of second metal magnetic particles;
A manufacturing method for coil components. The substrate preparation step includes:
a first molding step of forming a first molded part by applying a first molding pressure to a first magnetic material including a first magnetic powder, a second magnetic powder having an average circularity larger than that of the first magnetic powder, and a first thermosetting resin;
a second molding step of forming a molded body including the first molded part by covering the coil conductor installed in the first molded part and applying a second molding pressure smaller than the first molding pressure to a second magnetic material including the first magnetic powder, the second magnetic powder, and a second thermosetting resin;
The method for manufacturing a coil component according to claim 8 , comprising: The first molding pressure is 10 MPa or more and 100 MPa or less.
The method for manufacturing the coil component according to claim 9 . The second molding pressure is 10 MPa or more and 100 MPa or less.
The method for manufacturing a coil component according to claim 9 or 10. The method further includes a heating step of heating the molded body at a heating temperature that is equal to or higher than a thermosetting temperature of the first thermosetting resin and equal to or higher than a thermosetting temperature of the second thermosetting resin.
The method for manufacturing a coil component according to claim 8 or 9. The heating temperature is lower than 200° C.
The method for manufacturing a coil component according to claim 12.